JPH11312572A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide exothermic characteristic with very short time for reaching to the specified temperature region by forming a hollow part, in at least a resistant exothermic body part of the body of a heater comprising a resistant exothermic body and a ceramic insulating sheet in which the exothermic body is embedded. SOLUTION: A ceramic heater is formed in such a way that a resistant exothermic body 3 is embedded between a core material 1 having the shape of a pillar such as a round pillar or square pillar and an insulating sheet 2 covering the core material 1, and an electrode 4 is connected to each end of the resistant exothermic body 3 extending in the axial direction at both ends apart 180 degrees on the circumference of the core material 1. Each electrode 4 is exposed to the outside through a cut-out 5 formed in the insulating sheet 2. The formation of a hollow part 6 extending along a bus bar, between both bottoms 1a 1b is essential. The hollow part 6 may be passed through between the core material 1 and the bottoms 1a, 1b, but it is important that it be formed at least on the part of the resistant exothermic body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic heater having a resistance heating element embedded in ceramics.

[0002]

2. Description of the Related Art Ceramic heaters are widely used in oxygen sensors and glow systems for automobiles, and as heat sources for oil vaporizers such as semiconductor heaters and oil fan heaters.

[0003] As shown in FIG.
A resistance heating element 14 is embedded between a core material 11 and an insulating sheet 13 wound around the core material 11 via an adhesive layer 12, and both ends of the resistance heating element 14 Electrode provided on
15 and each connected. The end of the resistance heating element 14 and the electrode 15 are connected via a through hole provided below the electrode 15 of the insulating sheet 13. When power is supplied to the electrode 15 from the outside, the resistance heating element 14 generates heat, so that it functions as a heater.

[0004]

This ceramic heater is mounted, for example, inside the element of an oxygen sensor.
By generating heat, the ambient temperature of the element is kept constant, and the function of the element is avoided. In particular, since the oxygen sensor of a vehicle is ideally operated at the same time as the start of the engine, it is necessary to heat the element quickly. Therefore, the ceramic heater is required to have a performance of raising the temperature to a predetermined high temperature (area) in a short time.

Accordingly, an object of the present invention is to propose a ceramic heater having a heat generation characteristic in which the time to reach a predetermined temperature range is extremely short.

[0006]

According to the present invention, there is provided a ceramic heater comprising a resistance heating element and a ceramic insulating sheet in which the resistance heating element is embedded, wherein at least a resistance heating element portion of a body of the ceramic heater is hollow. It is a ceramic heater characterized by forming a portion.

[0007] In the above ceramic heater, it is advantageous in practice that the cross section of the ceramic heater body is substantially circular.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic heater according to the present invention will be described in detail with reference to FIG. That is, in this ceramic heater, a resistance heating element 3 is buried between a core material 1 having a columnar shape such as a cylinder and a prism, in the illustrated example, and an insulating sheet 2 covering the core material 1. Electrodes 4 are respectively connected to both ends of a resistance heating element 3 which extends in the axial direction on both sides separated by approximately 180 ° on the circumference of the material 1, and each is connected through a notch 5 formed in the insulating sheet 2. The electrode 4 is exposed outside. By the way, the through hole for connecting between the resistance heating element and the electrode, which has been required in the past, becomes unnecessary.

The core 1 has two bottom surfaces 1a and 1b.
It is essential to form a hollow portion 6 extending along the generatrix between them. Although this hollow portion 6 may be penetrated between the bottom surfaces 1a and 1b of the core material 1 as shown in the illustrated example, it is formed at least in the portion of the resistance heating element 3, in other words,
It is important that the portion of the core 1 around which the resistance heating element 3 is wound has a hollow portion 6 inside. Therefore, the hollow part 6
Does not necessarily need to be formed on the core material 1, for example, the core material 1
By omitting the part or all of
The inside of the resistance heating element 3 may be directly formed as the hollow portion 6. Due to the formation of the hollow portion 6, it is possible to give the ceramic heater excellent heat generation characteristics, particularly, heat generation characteristics in which the time required to reach a predetermined temperature range is extremely short.

Next, regarding the experimental results that led to finding a means for improving the heat generation characteristics of the ceramic heater,
Details will be described. That is, as shown in FIG. 3, a ceramic heater 8 was mounted in the element 7 of the oxygen sensor, and Ni-
The tip of the Cr thermocouple 9 was placed at the resistance heating element 3 of the ceramic heater 8 (position 6 to 7 mm from the tip of the core material), and the relationship between the elapsed time and the temperature during heating of the heater 8 was measured.
This measurement was performed for each of the ceramic heater having the structure shown in FIG. 2 (inventive example) and the ceramic heater having the same structure except that a solid core material having no hollow portion 6 was used (comparative example). A curve was determined. As shown in FIG. 4, it is clear that the provision of the hollow portion 6 in the core material 1 greatly reduces the time required to reach the scheduled heating temperature.

In the above experiment, heating was performed by using a high-melting point metal such as W, Re, and Mo as the resistance heating element of the ceramic heater and connecting to a 12 V power supply.

Further, the same experiment was performed by changing the size of the hollow portion 6 provided in the core material 1 (3.4 mmφ) to 0.9, 1.3 and 2.0 mmφ, and the result shown in FIG. 5 was obtained. It is clear from the figure that the heat generation characteristics are improved as the hollow portion 6 becomes larger. On the other hand, in the same experiment, the result of measuring the power consumption until the temperature reaches 700 ° C. clearly shows that the power consumption increases as the hollow portion 6 increases, as shown in FIG.

That is, the larger the hollow portion, that is, the smaller the volume of the heater heated by the resistance heating element,
It has been found that while the heat generation characteristics are improved, it is advantageous to reduce the size of the hollow portion to an appropriate range in order to reduce power consumption. In order to satisfy both of these characteristics, the diameter d of the hollow portion 6 and the diameter of the bottom surface of the core material 1 (the inner diameter of the resistance heating element when the core material 1 is omitted) are shown in FIG.
The ratio d / D to D is preferably set to 0.07 to 0.35.

The result shown in FIG. 4 is an example in which a through hollow portion is provided in the core material 1. If at least the hollow portion is formed in the resistance heating element 3, the same result as the above experimental result is obtained. The effect is obtained.

The cross-sectional shape of the hollow portion is preferably substantially circular from the viewpoint of manufacturability.

Here, the reason why the heat generation characteristics are improved by forming the hollow portion 6 at least in the resistance heating element 3 is not necessarily clear, but can be considered as follows. That is, by providing the hollow portion, the volume of the ceramic heated by the resistance heating element can be reduced, and as a result, the heat capacity can be reduced.

[0017]

According to the present invention, the ceramic heater can be provided with excellent heat generation characteristics, particularly, heat generation characteristics in which the time required to reach a predetermined temperature range is extremely short, so that the performance required of the ceramic heater can be sufficiently satisfied. .

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a conventional ceramic heater.

FIG. 2 is a perspective view and a front view showing a ceramic heater according to the present invention.

FIG. 3 is an explanatory diagram showing an experimental procedure.

FIG. 4 is a diagram showing heat generation characteristics of a ceramic heater.

FIG. 5 is a diagram showing heat generation characteristics of a ceramic heater.

FIG. 6 is a diagram showing power consumption when a ceramic heater generates heat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core material 2 Insulating sheet 3 Resistance heating element 4 Electrode 5 Notch 6 Hollow part 7 Element 8 Ceramic heater 9 Thermocouple

Claims (2)

[Claims] 1. A ceramic heater comprising a resistance heating element and a ceramic insulating sheet in which the resistance heating element is embedded, wherein a hollow portion is formed at least in a resistance heating element portion of a body of the ceramic heater. Ceramic heater. 2. The ceramic heater according to claim 1, wherein a cross section of the ceramic heater body is substantially circular.